The present invention relates to a structure for joining plate elements and a method for joining the same and, particularly, to a plate joining structure obtained by superposing an edge portion of one plate element on a joggled portion of another plate element and by welding a gap defined by the joggled portion and a terminal edge of the one plate element, and to a method for joining the plate elements.
In a known structure for joining plate elements of the above type, as disclosed in Japanese Patent Laid-open Pub. No. 63-56,366, a first plate element to be coupled with a second plate element is provided along its edge with a joggled portion formed contiguously to, and in an offset relation to a general portion of the first plate element in such a manner that the joggled portion will form a joining surface offset from the general portion and also form a shoulder between the general portion and the joggled portion, while the second plate element has an edge portion secured to the joining surface in a face-to-face contact therewith. A padding of weld fixedly secures the joggled portion and the edge portion together.
In the above structure for joining plate elements, the two plate elements can be welded and joined together without leaving on the surface of the plate elements any recess or impression that is caused by a spot welding electrode at the time of tack welding, since a movable electrode is brought into contact with and is pressed against an edge portion of one plate element for the spot welding and thereafter a padding weld is deposited into the space defined between two plate elements.
As will be described in detail later, however, local heating by the padding of weld results in generation of large thermal strains in the plate elements and causes concave thermal deformation after cooling. This requires such finishing work as repeated steps of hammering the back side of the joined structure and/or grinding the front side. This finishing work requires skilled workers and largely depends on the technique of the individual worker, causing deterioration in the quality of finishing and reduction in panel thickness of the joined structure. Furthermore, due to the necessity of repeated operation and large amount of the weld material remaining on the exterior of the surface of the joined structure, the number of finishing work steps increases and deterioration in the working environment may be induced. Moreover, the welded structure is not sufficiently rigid and strong.